1. Field of the Invention
The present invention relates to a passenger detecting system and a passenger detecting method, in particular, to a passenger detecting system and a passenger detecting method for placing an air bag of an air bag device in an inflatable state or a non-inflatable state corresponding to a seating pattern of a passenger or the like on an assistant driver's seat of a car.
2. Description of the Related Art
Generally, an air bag device is used to alleviate the shock to a passenger in a car in case of a collision as a safety device. In recent years, air bag devices are installed for an assistant driver's seat as well as a driver's seat.
As shown in FIG. 24, such an air bag device comprises a driver's seat side squib circuit, an assistant driver's seat side squib circuit, an electronic acceleration sensor (collision detecting sensor) GS, and a controlling circuit CC. The driver's seat side squib circuit is composed of a safety sensor SS1, a squib SQ1, and a semiconductor switching device SW1 (such as an electric field effect transistor) that are connected in series. The assistant driver's seat side squib circuit is composed of a safety sensor SS2, a squib SQ2, and a semiconductor switching device SW2 (such as an electric field effect transistor). The controlling circuit CC determines whether a collision takes place corresponding to an output signal of an electronic acceleration sensor (shock detecting sensor) GS and supplies the resultant signal to the gates of the semiconductor switching devices SW1 and SW2.
In the air bag device, in case of a collision of the car due to any pause, the switch contacts of the safety sensors SS1 and SS2 are closed by relatively weak acceleration, thereby placing the driver's seat side squib circuit and the assistant driver's seat side squib circuit in an operable state. When the controlling circuit CC determines that the car has collided corresponding to an output signal of the electronic acceleration sensor GS, the controlling circuit CC supplies signals to the gates of the semiconductor switching devices SW1 and SW2 causing the switching devices SW1 and SW2 to be turned on. Since currents flow in the respective squib circuits, the squibs SQ1 and SQ2 become hot, thereby causing the driver's seat side air bag and the assistant driver's seat side air bag to inflate. Thus, the passengers in the car are protected from the shock of the collision.
In the air bag device, as shown in FIG. 25A, when an adult P sits on a seat 1, in event of a collision, the passenger protection effect can be expected. However, as shown in FIG. 25B, when an infant SP sits on a child seat 2 that is secured to an assistant driver's seat 1 in such a manner that the infant SP faces the back rest of the assistant driver's seat (this seating pattern of the child seat is referred to as Rear Facing Infant Seat: RFIS), in case of a collision of the car, it is preferable not to cause the air bag to inflate. On the other hand, when an infant SP sits on the child seat 2 secured to the assistant driver's seat in such a manner that the infant SP faces the windshield of the car (this seating pattern of the child seat is referred to as Forward Facing Child Seat: FFCS), if the air bag inflates, the air bag may contact the face of the infant SP. Thus, as with the RFIS pattern, in case of a collision of the car, it is preferable not to cause the air bag to inflate.
To solve such problems, an air bag device as shown in FIG. 26 has been proposed. In this air bag device, a sensor SD that detects whether or not a passenger sits on the assistant driver's seat is disposed. A controlling circuit CC determines the seating pattern of a passenger on the assistant driver's seat and places the air bag in the inflatable state or non-inflatable state in case of a collision of the car. As examples of the sensor SD, a weight measuring sensor such as a piezoelectric device for measuring the weight and a CCD camera for photographing a passenger who sits on a seat and detecting whether the passenger is an adult P or an infant SP and whether the seating pattern of the passenger have been proposed.
When the weight measuring sensor is used, it is possible to determine whether a passenger on the seat is an adult P or an infant SP corresponding to weight categories. Corresponding to the measured result, the controlling circuit CC places the air bag in the inflatable state or non-inflatable state so as to prevent the passenger on the seat from be shocked in case of a collision. However, the weight of the passenger largely varies person by person. In addition, a fat infant may be heavier than a skinny person. Thus, the measured result of the weight measuring sensor is not accurate. In addition, with the weight measuring sensor, the controlling circuit CC cannot determine whether an infant sits on the seat in the RFIS pattern or FFCS pattern.
When the CCD camera is used, although the controlling circuit CC can accurately determine in what style a passenger sits on the seat, whether the passenger sits on the seat is an adult P or an infant SP, and whether an infant sits on a child seat in the RFIS pattern or FFCS pattern, the controlling circuit CC should process data photographed by the CCD camera and compare the resultant data with various patterns. Thus, the structure of the processing unit becomes complicated and the cost thereof becomes expensive.